Apparatus for treatment of contaminated liquids

ABSTRACT

A treatment vessel for separating contaminants from a base liquid is provided. The vessel comprises a first cylindrical portion, a frusto-conical portion, a second cylindrical portion and a conical portion, the conical portion having a bottom outlet arranged to discharge heavy contaminants from the vessel. Over time, the heavy contaminants settle on the sides of the conical and frusto-conical portions. In order to remove the settled contaminants, the vessel is provided with at least one clarified liquid inlet disposed at or proximate to the frusto-conical portion. The clarified liquid is sourced from either the treatment vessel itself, or another treatment vessel in the same system. The clarified liquid is reintroduced into the vessel in a manner so as to cause a downward circular flow to scour out the frusto-conical portion and the conical portion so as to assist in removal of heavy contaminants that settle on the sides thereof.

FIELD OF THE INVENTION

The present invention relates to an apparatus for treatment ofcontaminated liquids particularly, but not exclusively, treatment ofindustrial, agricultural and municipal effluent.

BACKGROUND OF THE INVENTION

Vessels for separating contaminants from liquids are well known in theart and are generally in the form of a cylindrical tank with a conicalbottom, where the apex of the conical bottom is lower than the outerside thereof.

Inlets may be positioned so as to produce a spiral flow of the liquid inthe vessel and outlets may be positioned at the bottom, top and sides ofthe vessel to enable the drawing off of various fractions of theseparated liquid stream, depending on its relative specific gravity.

For the purposes of this specification, a vessel or vessels ofaforementioned type will be hereinafter referred to as a “treatmentvessel” or “treatment vessels”.

The inlet of a treatment vessel is typically situated at the outer edgeof the treatment vessel, and is typically arranged in such a manner soas to introduce liquid tangentially and thereby create laminar, spiralflow within the treatment vessel. As the liquid nears the centre of thetreatment vessel, the speed decreases and the direction of the flow ischanged to a vertical up and down flow towards the top and bottomoutlets.

It is preferred that no spiral flow takes place at the centre part ofthe treatment vessel so as to allow the contaminants to separate.

Separation takes place within the treatment vessel as the speed of flowslows toward the centre of the treatment vessel. Thus, whilecontaminants are suspended at the rate of flow at the outer part of thetreatment vessel, these will be released as the speed of flow decreasestoward the centre of the treatment vessel and will separate into theirfractions depending on their specific gravity.

Separation can be aided by the prior addition of a variety of chemicalsubstances. The methods for introducing contaminated liquidstangentially into a treatment vessel so as to produce spiral flows andthe methods for operating such treatment vessels are well known.

It is often the practice to use more than one treatment vessel within asingle separator system where more than one operation is required withinthe separator system. Thus, one treatment vessel may be used forremoving those contaminants where the specific gravity of thecontaminants is heavier than the carrying liquid, and another treatmentvessel may be used to concentrate the contaminants removed.

A problem with existing treatment vessels used in separator systems isthat the heaviest contaminants are directed downward toward the apex ofthe conical bottom of the treatment vessel and can build up a plug whichdoes not flow out of the treatment vessel as desired.

The inventor of the present invention has previously provided a methodof mitigating plugging of the bottom outlet of the treatment vessel byreintroducing clarified liquid obtained from a treatment vessel withinthe separator system in a manner so as to produce a downward spiral flowto scour out the conical portion of the treatment vessel. However, ithas been found that the effectiveness of the method over prolongedperiods of time can sometimes be compromised by the formation of“rat-holes” within the settling sediment, since upon its mechanicalremoval the sediment adheres to the walls of the conical portion.Further, access to the bottom portion of the treatment vessel formaintenance and cleaning, in the eventuality of “rat-hole” formation cansometimes be very difficult.

The present invention seeks to mitigate the possibility of “rat-holing”and subsequent plugging in treatment vessels by the separation of heavycontaminants therein and which increases the efficiency of operation ofsame beyond that of prior treatment vessels and clarifiers.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there isprovided a treatment vessel for separating contaminants from a baseliquid treated therein, the treatment vessel comprising:

a first cylindrical portion;

a frusto-conical portion adjacent a lower end of the first cylindricalportion; and

a base portion comprising a second cylindrical portion adjacent a lowerend of the frusto-conical portion and a conical portion adjacent a lowerend of the second cylindrical portion, the conical portion having abottom outlet arranged to discharge heavy contaminants from thetreatment vessel;

a clarified liquid source derived from the treatment vessel or anothertreatment vessel in a treatment system; and

at least one clarified liquid inlet disposed at a side of the treatmentvessel to reintroduce clarified liquid into the treatment vessel fromthe clarified liquid source at, or proximate to, the frusto-conicalportion thereof;

wherein, in use, the clarified liquid is reintroduced in a manner so asto cause a downward circular flow to scour out the frusto-conicalportion and the conical portion of the base portion and assist inremoving heavy contaminants that accumulate adjacent the bottom outletof the treatment vessel.

In accordance with a second aspect of the present invention, there isprovided a treatment system for separating contaminants from a baseliquid treated therein, the system comprising;

a plurality of treatment vessels each including a frusto-conical portionand a base portion comprising a second cylindrical portion adjacent alower end of the frusto-conical portion and a conical portion adjacent alower end of the second cylindrical portion, the conical portion havinga bottom outlet arranged to discharge heavy contaminants from thetreatment vessel;

at least one clarified liquid source derived from one or more of thetreatment vessels, a clarified liquid inlet disposed at a side of the oreach treatment vessel to re-introduce the clarified liquid into thetreatment vessel from one of the clarified liquid sources at, orproximate to, the frusto-conical portion thereof;

wherein, in use, the clarified liquid is reintroduced in a manner so asto cause a downward circular flow to scour out the frusto-conicalportion and the conical portion of the base portion and assist inremoving the heavy contaminants that accumulate at a bottom outlet ofthe treatment vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a cross sectional side elevation of the vessel in accordancewith the first and second aspect; and

FIG. 2 is a plan view of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals and symbols refer tolike parts throughout, there is shown a treatment vessel 11. The firstand second aspects of the present invention are directed towards aseparator system using one or more treatment vessels 11.

The treatment vessel 11 comprises a right circular first cylindricalportion 13 having a frusto-conical portion 15 at a lower end thereof,and a right circular second cylindrical portion 17 having a conicalportion 19 at a lower end thereof.

The frusto-conical portion 15 has an apex 15 a lower than the side 15 bthereof. The second cylindrical portion 17 is integral with the apex 15a, the diameter of the second cylindrical portion 17 being coincidentwith the diameter of the apex 15 a. The conical portion 19 has an apex19 a lower than the side 19 b thereof.

The height of the first cylindrical portion 13 is preferably no morethan one and a half times the diameter of the first cylindrical portion13.

The diameter of the second cylindrical portion 17 is preferably fromabout 22% to about 40% of the diameter of the first cylindrical portion13.

The angle of inclination of side 19 b is preferably twice the angle ofinclination of side 15 b. Preferably, the angle of inclination of side19 b is about 60° and the angle of inclination of side 15 b is about30°.

In a preferred embodiment of the invention, the conical portion 19 isremovable from the treatment vessel 11. To this purpose, a lower edge ofthe second cylindrical portion 17 is preferably provided with a flangemember 18 a and an upper edge of the conical portion 19 is provided witha complementary flange member 18 b for mating thereof. The flangemembers 18 a, 18 b are fixed together with conventional fixing means.

A top 12 of the first cylindrical portion 13 is open and has an annulargutter 14 disposed around an upper edge 13 b of the first cylindricalportion 13, the latter defining an intermediate lip between the annulargutter 14 and the top 12 of the first cylindrical portion 13. In analternative embodiment of the invention, the annular gutter 14 isdisposed around an inside upper edge of the first cylindrical portion13. Inlets 21 for the vessel 11, defined by a pair of conduits 21 a and21 b, are tangentially disposed at the side of the first cylindricalportion 13 to introduce contaminated base liquid into the vessel 11 soas to produce a spiral flow of liquid within the treatment vessel 11.The conduits 21 a and 21 b are spaced apart from each other vertically,with the conduit 21 a disposed approximately midway along the length ofthe first cylindrical portion 13 of the treatment vessel 11, and theconduit 21 b disposed proximate to midway between the conduit 21 a andthe top of the frusto-conical portion 15 of the treatment vessel 11.Furtherstill, the openings of the conduits 21 a and 21 b are angularlyspaced apart around the circumference of the first cylindrical portion13 by approximately 90° as shown in FIG. 1 of the drawings.

It will be understood that in an alternative embodiment of the inventionthe vessel 11 is provided with only one inlet 21 tangentially disposedat the side of the first cylindrical portion 13 to introducecontaminated base liquid into the vessel 11 so as to produce a spiralflow of liquid within the treatment vessel 11.

A plurality of different sets of outlets are provided for the treatmentvessel 11. Bottom outlets 23 are disposed at the apex 19 a and aredefined by a pair of conduits 23 a and 23 b for discharging liquidthrough the apex 19 a from the treatment vessel 11. An upper outlet 25(or set of outlets not shown) is provided proximate to the top 12 of thetreatment vessel 11 and is defined by a conduit connected to a bottom ofthe annular gutter 14 in order to discharge liquid therefrom.

A further set of outlets 27 are disposed about the periphery of thefirst cylindrical portion 13 intermediate the top 12 and bottom of thefirst cylindrical portion 13. These outlets in the present embodimentare defined by four conduits 27 a, 27 b, 27 c and 27 d which are axiallyspaced apart along the treatment vessel 11 to discharge differentfractions of the liquid from within the treatment vessel 11, dependingupon the relative specific gravity thereof, as will be described in moredetail later.

Preferably, the vessel 11 is provided with flow modifying means 29comprising a pair of centrally disposed vanes 29 a, 29 b adjacent thetop of the first cylindrical portion 13. In the present embodiment, twovanes 29 a and 29 b are disposed in an orthogonally intersectingrelationship. The radial extent of the vanes 29 a, 29 b increasesprogressively towards the circumference of the first cylindrical portion13 as shown in FIG. 1, as the vane 29 extends axially towards the top 12of the vessel 11. The vanes 29 a, 29 b are fixedly mounted to the innerwall of the first cylindrical portion 13 at the outer radial ends of thefully extended radial portion thereof for fixedly disposing the flowmodifying means 29 within the treatment vessel 11.

Preferably, the vessel 11 is also provided with a cylindrical skirt 40depending from adjacent outer radial ends of the flow modifying means29, as shown in FIG. 1. A lowermost edge 42 of the cylindrical skirt 40is disposed adjacent the uppermost of the pair of conduits 21 a and 21b. The purpose of the cylindrical skirt 40 is to encourage flow ofseparated liquid, containing light weight contaminants in the form offlotation material, to be drawn up an outer side of the cylindricalskirt 40 so as to be discharged through the uppermost outlet 27 a.

In FIGS. 1 and 2 there are shown a plurality of first clarified liquidinlets 31 disposed at the side of the treatment vessel 11 proximate tothe frusto-conical portion 15 in a tangential manner so as toreintroduce the clarified liquid into the treatment vessel 11tangentially in this region. The first inlets 31 are connected to aclarified liquid source being a branch from one or more of the outletconduits 27 a, 27 b, 27 c or 27 d of another treatment vessel 11provided in the separator system or the upper outlet 25 of the sametreatment vessel 11.

As can be seen in FIGS. 1 and 2, the first inlets 31 are spacedequiangularly around the side 15 b of the frusto-conical portion 15 at aposition intermediate the top of the frusto-conical portion 15 and theapex 15 a Furthermore, the first inlets 31 are oriented slightly lowerat ends adjacent the treatment vessel 11 so that clarified liquidintroduced into the treatment vessel 11 therethrough is directed with adownward directional component towards the apex 15 a of thefrusto-conical portion 15 in a manner to be described in more detaillater.

In FIGS. 1 and 2 there are shown a plurality of second clarified liquidinlets 33 disposed at the side of the treatment vessel 11 proximate tothe second cylindrical portion 17. The second inlets 33 are oriented ina downward longitudinal manner so as to reintroduce the clarified liquidinto the treatment vessel 11 longitudinally in this region. The secondinlets 33 are connected to a clarified liquid source being a branch fromone or more of the outlet conduits 27 a, 27 b, 27 c or 27 d of anothertreatment vessel 11 provided in the separator system or the upper outlet25 of the same treatment vessel 11.

As can be seen in FIGS. 1 and 2, the second inlets 33 are spacedequiangularly around the second cylindrical portion 17 at a positionintermediate the top and the bottom of the second cylindrical portion17.

In a preferred embodiment of the present invention the first and secondinlets 31, 33 are spray nozzles which reintroduce the clarified liquidinto the treatment vessel 11 under pressure. Typically, for example,each spray nozzle would reintroduce clarified liquid into the treatmentvessel 11 at a flow rate of 17 L/minute at a pressure of 68 kPa. It willbe understood that the number of first and second inlets 31, 33 providedto the treatment vessel 11, and the flow rate and pressure under whichthey operate will vary according to the size of the treatment vessel 11and the sedimentary characteristics of the contaminated liquidsintroduced into the treatment vessel 11 for treatment.

The separator system of FIGS. 1 and 2 comprises one or more treatmentvessels 11, as described above. Accordingly, the conduits 31 a and 31 bare connected either to a clarified liquid source being a branch fromone or more of the outlet conduits 27 a, 27 b, 27 c or 27 d from atreatment vessel 11 disposed subsequently in the series of treatmentvessels 11 constituting the separator system, the upper outlet 25 of thesame treatment vessel 11, or both.

Now describing the manner of operation of the separator system,contaminated base liquid is supplied to a treatment vessel via theinlets 21.

In the case of a single treatment vessel separator system, the inlets 21are connected to some contaminated base liquid source and the outlets 25provide different fractions of the clarified decontaminated base liquid.

In the case of the separator system comprising a plurality of treatmentvessels 11, the treatment vessels 11 are connected in series so that theinlets 21 of all subsequent treatment vessels 11 are connected to one ormore of the outlets 27 or a preceding treatment vessel 11— or in thecase of a preceding treatment vessel dedicated to treating a low volumeof light contaminants, to the upper outlet 25 and/or in the case of apreceding vessel dedicated to treating a low volume of heavycontaminants, to the bottom outlet 23 b additionally or alternatively tothe outlets 27. Thus, the outlets 27 of all preceding treatment vessels11 in the series are connected to the inlets 21 of a subsequenttreatment vessel 11, additionally and/or alternatively to the outlets 25and 23 b, depending upon whether the treatment vessel 11 is dedicated tohandling low volumes of light or heavy contaminants, respectively.

In the interests of risk management, it is preferable that the separatorsystem comprise a plurality of treatment vessels 11 connected in seriesas described previously, wherein the series of connected vessels 11 arethemselves connected in a parallel configuration. In this way, thefailure of one treatment vessel 11 will not entirely interrupt processcontrol within the system. Furthermore, a parallel configuration ofseveral serially connected treatment vessels 11 allows for operationalflexibility in that one or more vessels 11 can be readily added orsubtracted from the system to account for volume capacity changes in atreatment plant.

The tangential positioning of the inlets 21 is provided to introducebase liquid containing heavy and light contaminants into the treatmentvessel 11 in a tangential manner so as to produce a circular flowtherein. Frictional forces between the circulating flows and theinternal surfaces of the treatment vessel 11 produce laminar flowswithin the circulating liquid which facilitate the displacement of theheavy and light contaminants, under gravity, through the liquid. Heavycontaminants, having a relative specific gravity greater than that ofthe residual decontaminated base liquid, travel down towards the apex 19a or the conical portion 19, whilst light contaminants, having aspecific gravity lighter than the contaminated base liquid, travelupward towards the top 12 of the treatment vessel 11.

This separation of heavy and light contaminants allows relativelyclarified, decontaminated base liquid to remain midway between the topand bottom of the first cylindrical portion 13, allowing this to bedrawn off and discharged via the outlets 27. As described, the outlets27 are spaced apart axially of each other to enable different fractionsof clarified decontaminated base liquid to be drawn off from thetreatment vessel 11. In this way, the treatment vessel 11 of the presentinvention affords a threefold separation of heavy contaminants, lightcontaminants such as in the form of flocculatory material, and clarifieddecontaminated base liquid.

Importantly, the first clarified liquid inlets 31 reintroduce clarifiedliquid to the treatment vessel 11 in a tangential manner, so as tocirculate the liquid containing heavy contaminants proximate to thefrusto-conical portion 15 of the treatment vessel 11 in a downwarddirection which causes a downward circular flow of liquid to scour outthe frusto-conical portion 15 and assist in removing the heavycontaminants accumulating at the bottom outlet 23 of the treatmentvessel 11.

Further, the removal of heavy contaminants which accumulate at thebottom outlet 23 of the treatment vessel 11 is also assisted byreintroduction of clarified liquid through the second inlets 33 in adownward direction to scour out the conical portion 19.

In this way, plugging of the apex 19 a and hence the bottom outlets 23is avoided by fluidising the heaviest contaminants continuously,enabling them to flow through one or other of the outlets 23 a or 23 b,which ever is connected into the system.

The scouring action produced by the flow of reintroduced clarifiedliquid is further assisted by the force of the flow of clarified liquidas it is reintroduced into the treatment vessel 11 under pressurethrough the spray nozzles at inlets 31, 33.

Furthermore, the accumulation of sediments on the frusto-conical portion15 and the conical portion 19 through “rat-holing” over prolongedperiods of time is minimised by the augmentation of the treatment vessel11 with the second cylindrical portion 17 and the conical portion 19,particularly since the angle of inclination of side 19 b is greater thanthe angle of inclination of side 15 b.

In the preferred embodiment of the invention, the conical portion 19 canbe easily removed by loosening the fixing means which hold flangemembers 18 a, 18 b together, thus providing ease of access to thefrusto-conical portion 15 of the treatment vessel 11 and the secondcylindrical portion 17, and the conical portion 19 for maintenance andcleaning purposes.

It should be appreciated that the scope of the present invention is notlimited to the particular embodiments herein described and that minormodifications or changes to the vessel design are envisaged to fallwithin the scope of the present invention and do not depart from thespirit of the same.

1. A treatment vessel for separating contaminants from a base liquidtreated therein, the treatment vessel comprising: a first cylindricalportion; a frusto-conical portion adjacent a lower end of the firstcylindrical portion; a second cylindrical portion adjacent a lower endof the frusto-conical portion; a conical portion adjacent a lower end ofthe second cylindrical portion, the conical portion having a bottomoutlet arranged to discharge heavy contaminants from the treatmentvessel; a clarified liquid source derived from the treatment vessel oranother treatment vessel in a treatment system; and a plurality of firstclarified liquid inlets disposed at a side of the treatment vessel toreintroduce clarified liquid into the treatment vessel from theclarified liquid source at the frusto-conical portion thereof; suchthat, in use, the clarified liquid is reintroduced in a manner so as tocause a downward circular flow to scour out the frusto-conical portionand the conical portion and to assist in removing heavy contaminantsthat accumulate adjacent the bottom outlet of the treatment vessel;wherein the treatment vessel is further provided with a plurality ofsecond clarified liquid inlets disposed at a side of the treatmentvessel to reintroduce clarified liquid into the treatment vessel fromthe clarified liquid source at the second cylindrical portion thereof;such that, in use, the clarified liquid is reintroduced in a manner soas to cause a downward flow to scour out the conical portion and toassist in removing heavy contaminants that accumulate adjacent thebottom outlet of the treatment vessel.
 2. The treatment vessel accordingto claim 1, characterized in that the first and second clarified liquidinlets are spaced equiangularly around the frusto-conical portion andthe second cylindrical portion, respectively.
 3. The treatment systemaccording to claim 2, characterized in that the first and secondclarified liquid inlets are spray nozzles.
 4. The treatment vesselaccording to claim 1, characterized in that the first and secondclarified liquid inlets are spray nozzles.
 5. The treatment vesselaccording to claim 1, characterized in that the angle of inclination ofa side of the conical portion is about twice the angle of inclination ofa side of the frusto-conical portion.
 6. The treatment vessel accordingto claim 5, characterized in that the angle of inclination of the sideof the conical portion is about 60° and the angle of inclination of theside of the frusto-conical portion is about 30°.
 7. The treatment vesselaccording to claim 1, characterized in that the diameter of the secondcylindrical portion is from about 22% to about 40% of the diameter ofthe first cylindrical portion.
 8. The treatment vessel according toclaim 1, characterized in that the conical portion is removable from thetreatment vessel.